add migration support for check constraints to MyXQL adapter

integration_test/myxql/constraints_test.exs

@@ -16,17 +16,8 @@ defmodule Ecto.Integration.ConstraintsTest do
         add :to, :integer
       end
 
-      execute(&positive_price_up/0, &positive_price_down/0)
-    end
-
-    defp positive_price_up do
-      # Only valid after MySQL 8.0.19
-      repo().query!("ALTER TABLE #{@table.name} ADD CONSTRAINT positive_price CHECK (price > 0);", [], [log: :info])
-    end
-
-    defp positive_price_down do
       # Only valid after MySQL 8.0.19
-      repo().query!("ALTER TABLE #{@table.name} DROP CONSTRAINT positive_price;", [], [log: :info])
+      create constraint(@table.name, :positive_price, check: "price > 0")
     end
   end
 

lib/ecto/adapters/myxql/connection.ex

@@ -1038,12 +1038,31 @@ if Code.ensure_loaded?(MyXQL) do
     def execute_ddl({:create_if_not_exists, %Index{}}),
       do: error!(nil, "MySQL adapter does not support create if not exists for index")
 
-    def execute_ddl({:create, %Constraint{check: check}}) when is_binary(check),
-      do: error!(nil, "MySQL adapter does not support check constraints")
+    def execute_ddl({:create, %Constraint{check: check} = constraint}) when is_binary(check) do
+      table_name = quote_name(constraint.prefix, constraint.table)
+      [["ALTER TABLE ", table_name, " ADD ", new_constraint_expr(constraint)]]
+    end
 
     def execute_ddl({:create, %Constraint{exclude: exclude}}) when is_binary(exclude),
       do: error!(nil, "MySQL adapter does not support exclusion constraints")
 
+    def execute_ddl({:drop, %Constraint{}, :cascade}),
+      do: error!(nil, "MySQL does not support `CASCADE` in `DROP CONSTRAINT` commands")
+
+    def execute_ddl({:drop, %Constraint{} = constraint, _}) do
+      [
+        [
+          "ALTER TABLE ",
+          quote_name(constraint.prefix, constraint.table),
+          " DROP CONSTRAINT ",
+          quote_name(constraint.name)
+        ]
+      ]
+    end
+
+    def execute_ddl({:drop_if_exists, %Constraint{}, _}),
+      do: error!(nil, "MySQL adapter does not support `drop_if_exists` for constraints")
+
     def execute_ddl({:drop, %Index{}, :cascade}),
       do: error!(nil, "MySQL adapter does not support cascade in drop index")
 
@@ -1059,12 +1078,6 @@ if Code.ensure_loaded?(MyXQL) do
       ]
     end
 
-    def execute_ddl({:drop, %Constraint{}, _}),
-      do: error!(nil, "MySQL adapter does not support constraints")
-
-    def execute_ddl({:drop_if_exists, %Constraint{}, _}),
-      do: error!(nil, "MySQL adapter does not support constraints")
-
     def execute_ddl({:drop_if_exists, %Index{}, _}),
       do: error!(nil, "MySQL adapter does not support drop if exists for index")
 
@@ -1256,6 +1269,17 @@ if Code.ensure_loaded?(MyXQL) do
     defp null_expr(true), do: " NULL"
     defp null_expr(_), do: []
 
+    defp new_constraint_expr(%Constraint{check: check} = constraint) when is_binary(check) do
+      [
+        "CONSTRAINT ",
+        quote_name(constraint.name),
+        " CHECK (",
+        check,
+        ")",
+        validate(constraint.validate)
+      ]
+    end
+
     defp default_expr({:ok, nil}),
       do: " DEFAULT NULL"
 
@@ -1413,6 +1437,9 @@ if Code.ensure_loaded?(MyXQL) do
     defp reference_on_update(:restrict), do: " ON UPDATE RESTRICT"
     defp reference_on_update(_), do: []
 
+    defp validate(false), do: " NOT ENFORCED"
+    defp validate(_), do: []
+
     ## Helpers
 
     defp get_source(query, sources, ix, source) do
@@ -1435,6 +1462,10 @@ if Code.ensure_loaded?(MyXQL) do
 
     defp maybe_add_column_names(_, name), do: name
 
+    defp quote_name(nil, name), do: quote_name(name)
+
+    defp quote_name(prefix, name), do: [quote_name(prefix), ?., quote_name(name)]
+
     defp quote_name(name) when is_atom(name) do
       quote_name(Atom.to_string(name))
     end

test/ecto/adapters/myxql_test.exs

@@ -1621,7 +1621,8 @@ defmodule Ecto.Adapters.MyXQLTest do
 
   # DDL
 
-  import Ecto.Migration, only: [table: 1, table: 2, index: 2, index: 3, constraint: 3]
+  import Ecto.Migration,
+    only: [table: 1, table: 2, index: 2, index: 3, constraint: 2, constraint: 3]
 
   test "executing a string during migration" do
     assert execute_ddl("example") == ["example"]
@@ -1963,23 +1964,6 @@ defmodule Ecto.Adapters.MyXQLTest do
     assert execute_ddl(drop) == [~s|DROP TABLE `foo`.`posts`|]
   end
 
-  test "drop constraint" do
-    assert_raise ArgumentError, ~r/MySQL adapter does not support constraints/, fn ->
-      execute_ddl(
-        {:drop, constraint(:products, "price_must_be_positive", prefix: "foo"), :restrict}
-      )
-    end
-  end
-
-  test "drop_if_exists constraint" do
-    assert_raise ArgumentError, ~r/MySQL adapter does not support constraints/, fn ->
-      execute_ddl(
-        {:drop_if_exists, constraint(:products, "price_must_be_positive", prefix: "foo"),
-         :restrict}
-      )
-    end
-  end
-
   test "alter table" do
     alter =
       {:alter, table(:posts),
@@ -2152,15 +2136,34 @@ defmodule Ecto.Adapters.MyXQLTest do
   end
 
   test "create constraints" do
-    assert_raise ArgumentError, "MySQL adapter does not support check constraints", fn ->
-      create = {:create, constraint(:products, "foo", check: "price")}
-      assert execute_ddl(create)
-    end
+    create = {:create, constraint(:products, "price_must_be_positive", check: "price > 0")}
 
-    assert_raise ArgumentError, "MySQL adapter does not support check constraints", fn ->
-      create = {:create, constraint(:products, "foo", check: "price", validate: false)}
-      assert execute_ddl(create)
-    end
+    assert execute_ddl(create) ==
+             [
+               ~s|ALTER TABLE `products` ADD CONSTRAINT `price_must_be_positive` CHECK (price > 0)|
+             ]
+
+    create =
+      {:create,
+       constraint(:products, "price_must_be_positive", check: "price > 0", prefix: "foo")}
+
+    assert execute_ddl(create) ==
+             [
+               ~s|ALTER TABLE `foo`.`products` ADD CONSTRAINT `price_must_be_positive` CHECK (price > 0)|
+             ]
+
+    create =
+      {:create,
+       constraint(:products, "price_must_be_positive",
+         check: "price > 0",
+         prefix: "foo",
+         validate: false
+       )}
+
+    assert execute_ddl(create) ==
+             [
+               ~s|ALTER TABLE `foo`.`products` ADD CONSTRAINT `price_must_be_positive` CHECK (price > 0) NOT ENFORCED|
+             ]
 
     assert_raise ArgumentError, "MySQL adapter does not support exclusion constraints", fn ->
       create = {:create, constraint(:products, "bar", exclude: "price")}
@@ -2173,6 +2176,37 @@ defmodule Ecto.Adapters.MyXQLTest do
     end
   end
 
+  test "drop constraint" do
+    drop = {:drop, constraint(:products, "price_must_be_positive"), :restrict}
+
+    assert execute_ddl(drop) ==
+             [~s|ALTER TABLE `products` DROP CONSTRAINT `price_must_be_positive`|]
+
+    drop = {:drop, constraint(:products, "price_must_be_positive", prefix: "foo"), :restrict}
+
+    assert execute_ddl(drop) ==
+             [~s|ALTER TABLE `foo`.`products` DROP CONSTRAINT `price_must_be_positive`|]
+
+    drop_cascade = {:drop, constraint(:products, "price_must_be_positive"), :cascade}
+
+    assert_raise ArgumentError,
+                 ~r/MySQL does not support `CASCADE` in `DROP CONSTRAINT` commands/,
+                 fn ->
+                   execute_ddl(drop_cascade)
+                 end
+  end
+
+  test "drop_if_exists constraint" do
+    assert_raise ArgumentError,
+                 ~r/MySQL adapter does not support `drop_if_exists` for constraints/,
+                 fn ->
+                   execute_ddl(
+                     {:drop_if_exists,
+                      constraint(:products, "price_must_be_positive", prefix: "foo"), :restrict}
+                   )
+                 end
+  end
+
   test "create an index using a different type" do
     create = {:create, index(:posts, [:permalink], using: :hash)}